I've been keeping a list of my unbuilt kits the easy way, manually in a loose leaf binder. Each page(s) starts with the nationality of the subject, U.S. aircraft, German aircraft, etc. I use columns as follows: subject, kit mfg., scale, comments, and carton or box number stored in. I also have one separate box for keeping all of the after-market items. As I build or use each item, I just cross it out with a single line.
Give each carton or box it's own number and mark all sides. This is a quick and easy system to maintain. I thought about putting this into a computer system, but since I've been doing it this way since the 1980s, why should I have to go through all of that data entry?
Do it the way that is best for you, but do it!, otherwise you will go crazy trying to find that one kit you remember from way back when.
Pete